Abstract: A twin disc type tool turret mechanism for CNC machines including a double layer of tool mounting discs attached respectively to two of a three-piece toothed ring-type registration and lock coupling. The front disc provides a number of mounting slots for external turning tools and the rear disc provides the same number of mounting seats for facing, OD turning or internal boring tools. A drive mechanism combined with a hydraulic control system incorporated in/on the turret housing facilitates unlocking, rotation, and relocking of the discs with the turret housing. The subject turret can also include provisions for attachment of revolving tools with an active spindle and an additional spindle motor for effecting the required processing operations. In addition, both OD and ID probes and a signal transmitting mechanism may be installed in both discs to accomplish in-process measurement of the workpiece.